STING RAY. 133 



nineteen inches; the snout short, thin, and a little turned up; 

 from it to the eye three inches and a half; the eye rather 

 small, and prominent; spiracles large, and passing forward under 

 the eye. At about the middle of the body it is much raised, 

 and from that part it slopes both forwards and behind; the 

 widest part at about six inches and a half from the snout, and 

 consequently before the middle; ventral fins nearly square pos- 

 teriorly. The tail thick and round from its origin to the place 

 of the spine, and from thence slender. Root of the spine five 

 inches and a half from the origin of the tail; the spine five 

 inches long, lying lengthwise; moderately sharp, grooved in 

 several lines, with a keel below, armed along each side with 

 a close-placed row of reversed points. A deep depression 

 along the middle of the back of the tail from its origin up- 

 wards there obsolete; two others on each side of the root of 

 the spine, passing up to the cross bones not far behind the 

 eyes; which lines, although fainter than the middle line below, 

 are more strongly marked above. The skin smooth; mouth and 

 teeth small. In one example the general colour was a dark 

 red, in another dusky yellow. 



It is a wise provision in the oeconomy of nature, that when 

 the dart has become blunted or otherwise useless, provision is 

 made for its being restored, by a loosening of its root of 

 attachment, when it drops off, and is replaced by a new one. 

 Whether this is done periodically, or at irregular intervals, is 

 not known; but it sometimes happens that the newly-formed 

 spear is well advanced in growth before its predecessor is 

 thrown off", and an instance of this sort enables us to remark 

 that both had their origin from the same root or gland. The 

 older spear was the longer, being seven inches long in a fish 

 the extreme length of which was three feet, hanging rather 

 loosely; while the new, which protruded under the other, 

 closely adhered for half an inch, and was of softer consistence 

 near its root. Professor Owen refers to Agassiz, as pointing 

 out the close resemblance of the microscopic structure of the 

 bone of this spine or dart, and the dentine of the teeth of 

 the same fishes; they are both hardened by an outer layer of 

 modified dentine, but as hard as enamel. 



Mr. Dillwyn (Fauna of Swansea,) mentions an instance of 

 the occurrence of two spines in a Sting E.ay caught near 

 VOL. I. U 



